Traditionally, engine oils (transmission oil, power steering oil, etc) are cooled by oil coolers. These oil coolers are located either within the water tank of a radiator (called “water-cooled in-tank” oil cooler) or in front of condensers (air-cooled oil cooler). In some cases, when the thermal cooling requirement is high, either in-tank water-cooled oil cooler or air-cooled oil cooler cannot satisfy the increased cooling requirement, and two separate oil coolers must be used.
The traditional oil cooler layout has several advantages: the in-tank oil cooler has good cold start in the winter, as oil is warmed by water inside radiator. Air-cooled oil coolers have flexibility of location. The disadvantages of a separate air-cooler are decreased by employing an air-cooled oil-cooler within a combo-cooler, which leads to lower cost, as well as huge packaging savings.
The use of fins in air-cooled type heat exchangers for automobiles is known. Fins reduce the temperature of various working fluids, including engine coolant, engine lubricating oil, air conditioning refrigerant, and automatic transmission fluid, among others. The heat exchanger typically includes a plurality of spaced fluid conduits or tubes connected between an inlet and an outlet, and a plurality of heat exchanging fins interposed between adjacent tubes or conduits. Air is directed across the fins via a cooling fan or the motion of the automobile. As the air flows across the fins, heat in the fluid flowing in the tubes is conducted through the walls of the tubes into the fins and transferred or “exchanged” into the airflow.
In order to achieve high production simplicity to meet ever increasingly heat exchanger thermal requirements, for most heat exchangers, it is preferable that fins or separators are used. The fins or separators may touch or connect similar types of tubes, (i.e. the fins or separators may ‘touch’ or ‘connect’ condenser tubes to condenser tube, or oil tube to oil tubes), or different tubes (for example condenser to oil tubes, etc.).
One of the primary goals in heat exchanger design is to achieve the highest possible thermal efficiency. Thermal efficiency is measured by dividing the amount of heat that is actually transferred by the heat exchanger in a given set of conditions (amount of airflow, temperature difference between the air and fluid, etc.) by the theoretical maximum possible heat transfer under those conditions. An increase in the rate of heat transfer, therefore, results in greater thermal efficiency. Heat transfer is also affected by the air pressure drop associated with the change in airflow direction caused by the fins. A greater air pressure drop results in less heat transfer. Various types of fin designs have been disclosed in the prior art with the object of increasing the heat exchanger efficiency by making improvements in the fins and airflow pattern.
One of the advantages of multi-exchanger or combo-coolers is that multiple heat exchangers (multi-exchangers) can be employed which share, for example, the same frontal area or space of a vehicle. Multi-exchanger or combo cooler heat exchangers have two or more heat exchanger parts comprising fluid conduits or tubes wherein different fluids can flow within the different tubes. Combo coolers, therefore, encounter manufacturing difficulties, and, therefore, there has been a need to find solutions to make production of said coolers more uniform, and therefore, increase efficiency of production.
The prior art has shown a fin preference towards using the same types of fins or separators in heat exchangers. Because the whole multi-exchanger can be assembled at the same time, the use of one type of manifold, core and fin leads to a saving in assembling cost (core assembly, brazing), as well as material cost (only one pair of manifold, only one pair of brackets).
Though using the same type of fins for both condenser and oil-cooler can be done for simplicity and ease of production, it is clearly not sufficient or optimal from a product design point for heat exchanger applications. It continues to be desirable to increase overall heat exchanger efficiency. Fin design continues to play an important role in increasing heat exchanger efficiency. In other words, when a ‘condenser fin’ is optimized, the same fin for oil cooler is not optimized, and vice-versa. It is one of the objectives of the present invention to provide for optimized heat exchanger efficiency in multi-exchangers or combo coolers. By going against the prior art usage of same type fins throughout the heat exchanger in favor of employing different type fins on different parts of the multi-exchanger or combo-cooler, optimization of overall heat exchanger efficiency can be achieved based on the different characteristics of the multi-exchanger.